After their first receivers with digital frequency readout based on a
conventional designed double conversion set equipped with a frequency counter,
Panasonic presented the DR-31 / RF-3100 in 1982: a PLL synthesized receiver.
The operation scheme of the DR-31 / RF-3100 is absolutely straightforward, the good
performance on shortwave and ease of operation make this set a good catch
when found on the used market for a reasonable price.

Double conversion, ZF 2 MHz, 455 kHz

Digital frequency display, 1 kHz, coverage 30 kHz - 30 MHz

AM, CW, USB/ LSB, FM (UKW)

Sensitivity SSB < 0.5 uV

Selectivity -6 dB
3,8 / 8 kHz

S Meter, RF Gain

The RF-3100 follows a travel receiver design, with all controls located
on it's front panel, it looks like a small desktop receiver and can also be
used for this purpose. With it's dimensions of 37,1 x 12,2 x 24,1 cm and it's weight of
3,2 kg it s too bulky to be used as a travel portable nowadays.
The RF-3100 can be powered from 110-125 / 220-240 V mains or 8 UM-1 / mono cells,
the mains cable can be stored in a small compartment at the bottom face of the radio.
The set is equipped with a carrying strap, as many travel radios from the eighties did.

The left part of the front panel space is taken by the 9 cm diameter speaker.
At the corresponding front panel space on the right, You find the huge tuning knob
on the on/off pushbutton.
All other controls are located in the middle segment of the front panel: the display
section with the analog signal strength meter, a red LED indicating sufficient
battery (or mains) power and the blue fluorescent frequency display - the frequency
is displayed wit ha resolution of 1 kHz. At the right, You find the band switch,
on the European model with the setting VHF / FM band, LW (longwaves), MW (mediumwaves)
and 29 shortwave bands, 1 MHz wide each. Three pushbuttons just below the frequency
display switch off the meter illumination and the frequency counter for power saving
reasons, switch the wide and narrow I.F. filter and activate the BFO.
In the bottom row of controls, You find from the left the headphones jack,
the volume control, a double control for separate bass and treble, an R.F. gain
control which will act rather as an attenuator, as the automated gain control
cannot be switched of for manual gain control, and the PFO pitch control.

On the back of the receiver, You find the connectors for a long wire and a
symmetric dipole antenna, a switch to activate the internal telescopic antenna
and an DIN audio input / output jack.

With it's ten controls, the mains switch included, the operation of the RF-3100
is very simple and easy to learn: connect to mains, pull out the telescopic
antenna (the switch at the rear should be set to telescopic antenna), press the
power button and the red power LED will light and You hear a noise from the
speaker. Use the shortwave band segment switch for the first (MHZ) digit
of the desired shortwave frequency, use the main tuning control to tune in
to the kHz digits, when You arrive at 1 5 5, You should hear Vienna's shortwave
signal.
The sensitivity is very good with the internal telescopic antenna. The receiver
does not tolerate lond wire antennas to well: in crowded bands (like the 49, 31 or 25
m shortwave band) during the night hours, the receiver front end tends to overload,
so You must use the R.F. gain control to prevent Your signal beeing covered up
from adjacent strong stations.
The two I.F. filters have not really steep skirts, but the are well suited for
shortwave broadcast stations reception, the narrow filter will separate two
5 kHz channels nicely.
SSB reception using the BFO reception is possible, but it cannot really be
enjoyed as the radio showas a significant drift: according to the manual, it
should be 500 Hz after warm up, I found my set drifting 2 - 4 kHz during an hour.

According to the age and the design of the receiver, a clock/timer and
digital frequency memories are lacking; as a simple shortwave and VHF receiver,
the RF-3100 does it's job really well and can be recommended when found for
a reasonable price on the used market as an entry or secondary receiver.